A cold rolled and annealed steel sheet includes by weight: 0.6<C<1.3%,15.0<Mn<35%, 6.0<Al<15%, Si<2.40%, S<0.015%, P<0.1%, N<0.1%, iron and inevitable impurities, optionally one or more of Ni, Cr and Cu in an individual amount of up to 3% and optionally one or more of B, Ta, Zr, Nb, V, Ti, Mo, and W in a cumulated amount of up to 2.0%, a microstructure of the sheet comprising at least 0.1% of intragranular kappa carbides, at least 80% of the kappa carbides have an average size below 30 nm, the remainder being made of austenite, an average grain size of the austenite being below 6 μm, an average aspect ratio of the austenite being between 1.5 and 6, an average grain size of the ferrite, when present being below 5 μm, and an average aspect ratio of the ferrite, when present, being below 3.0.

The present invention relates to an ultra-high strength, hot-dip galvanized steel sheet having excellent surface quality and coating adherence and to a method for manufacturing thereof, the ultra-high strength, hot-dip galvanized steel sheet comprising: 0.1-0.3% by weight carbon (C); 0.1-2.0% by weight silicon (Si); 0.005-1.5% by weight aluminum (Al); 1.5-3.5% by weight manganese (Mn); 0.04% by weight or less phosphorus (P) (excluding 0% by weight); 0.015% by weight or less sulphur (S) (excluding 0% by weight); 0.02% by weight or less nitrogen (N) (excluding 0% by weight); the balance being Fe; and other inevitable impurities, and further comprising 0.01 wt.% to 0.07 wt.% of at least one kind of element selected from the group consisting of bismuth (Bi), tin (Sn) and antimony (Sb).

A steel sheet for cans has a chemical composition containing, by mass %, C: 0.015% or more and 0.150% or less, Si: 0.04% or less, Mn: 1.0% or more and 2.0% or less, P: 0.025% or less, S: 0.015% or less, Al: 0.01% or more and 0.10% or less, N: 0.0005% or more and less than 0.0050%, Ti: 0.003% or more and 0.015% or less, B: 0.0010% or more and 0.0040% or less, and the balance being Fe and inevitable impurities. The steel sheet has a microstructure including a ferrite phase as a main phase and at least one of a martensite phase and a retained austenite phase as a second phase, the total area fraction of the second phase being 1.0% or more, and the sheet has a tensile strength of 480 MPa or more, a total elongation of 12% or more, and a yield elongation of 2.0% or less.

A steel sheet for two-piece cans is suitable not only for drawing and ironing, but also for forming beads or geometric shapes on a can body and can be preferably used to form a special-shaped two-piece can. The steel sheet for two-piece cans contains, in mass %, C: 0.020% to 0.080%, Si: 0.04% or less, Mn: 0.10% to 0.60%, P: 0.02% or less, S: 0.015% or less, Al: 0.010% to 0.100%, and N: 0.0005% to 0.0030%, the balance being Fe and unavoidable impurities. The steel sheet has a tensile strength of 480 MPa or more, an elongation of 7% or more, a yield elongation of 3% or less, and a ferrite grain size of less than 6 μm.

A steel sheet for a crown cap having sufficient strength and formability suitable for forming crown caps even when reduced in gauge, and a method for producing the steel sheet for a crown cap. The steel sheet for a crown cap having a composition that includes, in terms of % by mass: C: 0.002% or more and 0.010% or less, Si: 0.05% or less, Mn: 0.05% or more and 0.30% or less, P: 0.030% or less, S: 0.020% or less, Al: less than 0.0100%, N: 0.0050% or less, and the balance being Fe and unavoidable impurities. The C content is more than 0.003% when the Al content is 0.005% or more. The yield strength in the rolling direction is 500 MPa or more. The average Lankford value is 1.3 or more.

A high-strength steel sheet includes a chemical composition including: by mass %, C: 0.080 to 0.500%, Si: 2.50% or less, Mn: 0.50 to 5.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance: Fe and inevitable impurities. The high-strength steel sheet satisfying a predetermined formula has a microstructure in a region from ⅛t to ⅜t from a steel sheet surface. The microstructure includes: by volume %, 20% or more of acicular ferrite, 20% or more of an island-shaped hard structure including residual austenite, 2% to 25% of residual austenite, and 20% or less of aggregated ferrite.

A cold rolled and annealed steel sheet including by weight: 0.6<C<1.3%, 15≤Mn<35%, 6≤Al<15%, Si≤2.40%, S≤0.03%, P≤0.1%, N≤0.1%, possibly one or more optional elements chosen among Ni, Cr and Cu in an individual amount of up to 3% and possibly one or more elements chosen among B, Ta, Zr, Nb, V, Ti, Mo, and W in a cumulated amount of up to 2.0%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, the microstructure of the sheet including of ordered ferrite between 1% and 10%, optionally of up to 10% of kappa carbides, the remainder being made of austenite, and, the density of the steel sheet being equal or below 7.2 and the FWHM for the austenite matrix is between 0.700 and 1.100.

A high-strength steel sheet excellent in formability, toughness and weldability has a chemical composition including: by mass %, C: 0.05 to 0.30%, Si: 2.50% or less, Mn: 0.50 to 3.50%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 2.500%, N: 0.0150% or less, O: 0.0050% or less, and the balance consisting of Fe and inevitable impurities. The high-strength steel sheet has a microstructure in a region from ⅛t (t: sheet thickness) to ⅜t (t: sheet thickness) from a steel sheet surface, the microstructure including: by volume %, acicular ferrite (3): 20% or more, and martensite (4):10% or more, aggregated ferrite: 20% or less, residual austenite: 2.0% or less, and the martensite satisfies a formula (A),

[00001]$\begin{array}{cc}\underset{i=1}{\overset{5}{.Math.}}\frac{d_i}{{a_i}^{1.5}}\le 10.0& \left(A\right)\end{array}$

A method for the manufacture of a TWIP steel is provided including: (A) feeding of a slab comprising by weight: 0.5<C<1.2%, 13.0≤Mn<25.0%, S≤0.030%, P≤0.080%, N≤0.1%, Si≤3.0%, 0.051%≤Al≤4.0%, 0.1≤V≤2.5%, and on a purely optional basis, one or more of Nb≤0.5%, B≤0.005%, Cr≤1.0%, Mo≤0.40%, Ni≤1.0%, Cu≤5.0%, Ti≤0.5%, 0.06≤Sn≤0.2%, the remainder of the composition being made of iron and inevitable impurities resulting from the elaboration, (B) reheating the slab and hot rolling the slab to provide a hot rolled slab, (C) coiling the hot rolled slab to provide a coiled slab, (D) first cold-rolling the coiled slab to provide a first cold rolled slab, (E) recrystallization annealing the first cold rolled slab such that an annealed steel sheet having an UTS.sub.annealed is obtained and (F) second cold-rolling the annealed steel sheet with a reduction rate CR % that satisfies the following equation A: 1216.472−0.98795*UTS.sub.annealed≤(−0.0008*UTS.sub.annealed+1.0124)*CR %.sup.2+(0.0371*UTS.sub.annealed−29.583)*CR %.

A method for the manufacture of a cold rolled, recovered TWIP steel sheet coated with a metallic coating is provided including the following steps: (A) the feeding of a slab having the following composition: 0.1<C<1.2%, 13.0≤Mn<25.0%, S≤0.030%, P≤0.080%, N≤0.1%, Si≤3.0%, and on a purely optional basis, one or more elements such as Nb≤0.5%, B≤0.005%, Cr≤1.0%, Mo≤0.40%, Ni≤1.0%, Cu≤5.0%, Ti≤0.5%, V≤2.5%, Al≤4.0%, 0.06≤Sn≤0.2%, the remainder of the composition making up of iron and inevitable impurities resulting from elaboration; (B) Reheating such slab and hot rolling it; (C) A coiling step; (D) A first cold-rolling; (E) A recrystallization annealing; (F) A second cold-rolling; and (G) A recovery heat treatment performed by hot-dip coating.